An illustration is visualization such as a drawing, painting, photograph or other work of art that is created (usually in the form of a work made for hire) to elucidate or decorate textual information (such as a story, poem or newspaper article) by providing a visual representation.
Illustrators use variety of media to give form to visual ideas, stories and information; illustration can therefore be defined as communication through image making.
Image editors are intended for outputting bitmap-based graphics.
When working with vector objects in a bitmap editing program, they only preserve their vector-like qualities as you work in that particular software, saving your files in the program's native format. Once you want to output your documents from image editor to use in other software, you are generally limited to bitmap-based formats.
Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical equations, to represent images in computer graphics.